Magnetic resonance imaging (MRI), a non-invasive technique, is extensively used in biomedical research.
Diffusion MRI is a technique that is used to measure water mobility within tissues. The diffusion pattern of water molecules in tissues reflects tissue microstructure, such as tumor response to treatment. Diffusion MR images (i.e., diffusion weighted (DW) images) are typically acquired by single-shot echo-planar imaging (EPI) sequences, which are susceptible to inhomogeneity of the magnetic field (B0 field), resulting in signal loss and geometric distortion. Several methods were developed to cope with susceptibility artifacts, such as gradient compensation, advanced shimming techniques, modified pulse sequences, and post processing corrections. However, most of the proposed methods require dedicated MR pulse sequence editors or sophisticated calibration algorithms, which are not readily available for commercial scanners. Alternatively, Fluorinert™, a proton free perfluorinated electronic liquid, has been proposed to effectively reduce susceptibility artifacts by homogenizing the B0 field around the target tissue.
The biological meaning of the acquired images (DW images) has to be analyzed by a thorough histological examination. Thus, after acquiring the DW images, the target tissue need be embedded in an embedding medium, such as an optimal cutting temperature (OCT) compound, for cryostat sectioning (frozen sectioning).
However, it is difficult to correlate histological sections obtained by a frozen sectioning procedure with the DW images because of the distortion of the DW images and differences in section angle and thickness.
Furthermore, if the target tissue is embedded in the Fluorinert™ electronic liquid for a diffusion MRI examination, it need be removed from the Fluorinert™ electronic liquid and then embedded in another embedding medium for cryostat sectioning.